This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-287719, filed Sep. 21, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a magnetic disk apparatus, particularly, to a magnetic disk apparatus equipped with a humidity controller for controlling the humidity within a casing.
2. Description of the Related Art
In general, a magnetic disk apparatus, e.g., a hard disk drive (hereinafter referred to as xe2x80x9cHDDxe2x80x9d), comprises, for example, a magnetic disk, a spindle motor for rotating the magnetic disk, a magnetic head for writing/reading data in and from the magnetic disk, a head suspension assembly for supporting and moving the magnetic head, and a VCM for driving the head suspension assembly. These members of the magnetic disk apparatus are housed in a casing of a substantially hermetic structure. Where the casing is of a hermetic structure, the floating operation of the magnetic head relative to the magnetic disk can be stabilized in the writing/reading step. In addition, it is possible to prevent dust or the like from entering the casing.
Also, where the casing is of a substantially hermetic structure, the pressure inside the HDD is rendered different from the atmospheric pressure by the rapid change in the environmental temperature so as to bring about breakage of the casing. As a measure against the breakage of the casing, the casing is provided with fine holes allowing the atmosphere within the casing to communicate with the outer atmosphere. Also, air filters for preventing the dust from entering the casing from the outside are mounted on these fine holes.
On the other hand, where the casing is of a substantially hermetic structure, though fine holes are formed in the casing, a long time is required for replacing the air inside the HDD by the outer atmosphere, with the result that big influences are given to the change in the temperature and the change in the humidity of the HDD. To be more specific, the inner space of the HDD after operation for a long time under a high temperature state or under a high temperature and high humidity state comes to maintain a certain stable constant temperature. If the HDD is put in a normal environment, e.g., under the temperature of 25xc2x0 C. and the humidity of 55%, the temperature inside the HDD is gradually changed to the temperature of the general environment. However, since the moisture inside the HDD does not escape to the outside of the HDD, the relative humidity inside the HDD is increased to reach 90% or more in accordance with the temperature drop. As a result, dew is formed on the magnetic disk and on the surface of the magnetic head. What should be noted is that impurities tend to be dissolved in the dew so as to be adsorbed on the magnetic head and the magnetic disk, with the result that the metal part tends to be corroded.
As a measure for preventing dew formation, Japanese Patent Disclosure (Kokai) No. 5-12848 discloses an HDD provided with a humidity control apparatus comprising a moisture absorbing agent and a heater. However, in the HDD disclosed in this prior art, the moisture absorbing agent is kept in contact with the air inside the HDD. As a result, it is impossible for the moisture absorbing agent to absorb the moisture efficiently when the atmosphere inside the HDD has the highest humidity. Further, since the HDD is provided with a heater, the entire apparatus tends to be rendered bulky. At the same time, the heater provides a heat source so as to give detrimental effects to the internal mechanism of the HDD.
It is also conceivable to allow the inner atmosphere of the HDD to communicate with the outer atmosphere only when the inner atmosphere has a high humidity. In this case, however, the air circulation within the HDD is not satisfactory because the HDD has a complex inner structure, resulting in failure to obtain a desired effect.
An object of the present invention, which has been achieved in view of the situation described above, is to provide a magnetic disk apparatus, which prevents the formation of dew within the casing, so as to improve reliability.
According to an aspect of the present invention, there is provided a magnetic disk apparatus, comprising: a magnetic disk; a motor configured to support and rotate the magnetic disk; a magnetic head configured to write/read information to/from the magnetic disk; a casing of a substantially hermetic structure, which houses the magnetic disk, the motor and the magnetic head; and a humidity controller arranged within the casing and configured to control the humidity within the casing; the humidity controller including a container containing a moisture absorbing agent, an air communication port that permits communication between the inner space of the casing and the inner space of the container, and an opening-closing control section for opening-closing the air communication port in accordance with the humidity within the casing; and the opening-closing control section being arranged in the container and including a humidity sensitive member that is elongated or shrunk in accordance with the humidity to open-close the air communication port.
According to another aspect of the present invention, there is provided a magnetic disk apparatus, comprising a magnetic disk; a motor configured to support and rotate the magnetic disk; a magnetic head configured to write/read information to/from the magnetic disk; a casing of a substantially hermetic structure, which houses the magnetic disk, the motor and the magnetic head; and a humidity controller arranged within the casing and configured to absorb the moisture within the casing when humidity within the casing has exceeded a predetermined upper limit and for releasing the absorbed moisture into the casing atmosphere when the humidity within the casing has been lowered to a value smaller than a predetermined lower limit.
Additional objects and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.